Is that your only seahorse, one of my males would flashe back and fouth light to dark for about thirty min. every morning to attract his female. They would then join tails and sort of dance. He will turn almost white, then back to grey. She is always light, so I think he tries to look like her. He did this for about a year. Sadly, I recently purchased a new seahorse that brought a flesh-eating bacteria into my tank and I lost my female. My male has not yet once changed color at all since her death. That has been at least three months ago. That is the only color change I have ever had.